is there a fuel pump access plate in the trunk compartment for a 95 firebird 3.8 base model we hear fuelpump come on with zero fuel pressure at the fuel rail

First you need some gas in the tank so you can do some testing with a fuel pressure gauge. You must have check it some already to know that there is Zero fuel pressure at the rail. So even if the fuel regulator was stuck open, bad, you should register some sort of fuel pressure at the rail. So it looks like you'll be replacing the fuel pump first. But going back to one of your questions, yes there is a cut off switch for the gas. But it is only electrical. You say you can hear the fuel pump run so I doubt it is that. Also there is a strainer on the fuel pump you should replace also. Fuel pressure should be 30 to 44 lbs. and a dead head fuel pressure should be a min. of 47 lbs.

Oh, and change the fuel filter before you do any more testing.